1. Field of the Invention
The present invention relates to a semiconductor memory device, more particularly, to a semiconductor memory device enabling selection and change of the output organization.
2. Description of the Related Art
In recent years, various types of semiconductor memory devices have been developed and marketed in accordance with various requirements of users. Note, in the prior art, it requires a large amount of cost and a long period to develop new semiconductor memory devices, even when the differences between the new semiconductor memory devices differ only the output organizations (word-bit organizations) in the same memory matrix.
In the related art, there has been provided a semiconductor memory device enabling a reconfigurable organization, e.g., 4 mega word.times.1 bit (4M.times.1) and 1 mega word.times.4 bit (1M.times.4) organizations in a 4M-bit memory device. In this semiconductor memory device, the selection from the 4M.times.1 organization and the 1M.times.4 organization is carried out in accordance with the requirements organization in the manufacturing (maker side) or working stage (user side). Namely, this semiconductor memory device can be used both for .times.1 and .times.4 organizations without having to design and produce exclusive masks, wiring patterns, and the like. Therefore, the development period and required cost can be largely decreased.
In recent years, a capacity of a semiconductor memory device has been largely increased in accordance with improvements of semiconductor production technique, and the like. Therefore, a required time for testing the semiconductor memory device should be lengthened.
The semiconductor memory device enabling to select between the .times.1 and .times.4 organizations can realize to decrease the testing time by carrying out the memory test at .times.4 organization. In this case, for instance, the semiconductor memory device is provided as a one-bit output organization memory device, and the four-bit output organization is electrically reconfigured for carrying out the memory test.
In the prior art, a semiconductor memory device enabling to set a one-bit output organization (.times.1 organization) and a four-bit output organization (.times.4 organization) of output data has been provided. However, in the prior art semiconductor memory device, switch units formed by MOS transistors are employed to change the output organization. Therefore, due to the ON resistance (turn-ON resistance) of the MOS transistors that form the switch units as well as wiring capacitance, the prior art semiconductor memory device has a large delay in data transmission, and thus a high speed operation (high speed reading) cannot be realized.